Methods of using fuel bundle groups as evaluation constraints

ABSTRACT

A method of fuel bundle consideration in a reactor. The method includes creating or editing bundle groups including fuel bundles.

PRIORITY STATEMENT

This divisional application claims priority under 35 U.S.C. § 121 toco-pending application Ser. No. 11/128,354, filed May 13, 2005, theentire disclosure of which is herein incorporated by reference.

BACKGROUND

The information setting forth the placement of fuel bundles, each ofwhich has various attributes, in a nuclear reactor core is referred toas the loading map. In conventional core design, creating the loadingmap is an experienced based, trial and error, iterative process.

The core designer generally receives plant specific critical to qualityfactors such as plant cycle energy requirements, thermal and operationallimits, shut down margins, etc. The core designer will also haveinformation on the layout of the reactor core; namely, an indication ofthe how the nuclear fuel bundles are positioned within the core. Some ofthe critical to quality factors may even concern the layout. Forexample, the core designer may receive input requiring the positioningof certain fuel bundles within the layout.

Given this information, the core designer then makes a guess, based onexperience and various rules of thumb he may have developed over time,on the initial positioning of fuel bundles in the reactor core.Specifically, the core designer guesses how many fresh fuel bundles toplace in the core, and what types of fresh fuel bundles to use. A freshfuel bundle is a fuel bundle that has not been exposed. Fuel bundles ofthe same type have substantially the same attributes. The attributesinclude but are not limited to: uranium loading, average enrichment,gadolinia loading, number of axial zones, product line, andthermal-mechanical characteristics of the fuel bundles. Different typesof fresh fuel bundles have one or more different attributes. In decidinghow many fresh fuel bundles to use, the core designer is also decidinghow many of the fuel bundles currently in the core to reuse. Reusing thefuel bundles currently present in the core can mean leaving a fuelbundle in its existing location, or moving the fuel bundle to adifferent location in the core.

As part of the core design, the core designer also determines otheroperational parameters of the reactor core such as control bladepositions, core flow, etc. Having specified these operational controlparameters, a Nuclear Regulatory Commission (NRC) licensed simulationprogram is then run on the initial core design. Based on the results ofthe simulation, the core designer utilizes experience and rules of thumbto fix perceived problems in the design and, in general, improve thedesign; particularly with respect to the critical to quality factors.These changes may include changing the loading map. The process repeatsuntil the core designer is satisfied with the design.

SUMMARY OF THE INVENTION

In an embodiment of the present invention, at least one fuel bundlewithin a core is assigned into one of a plurality of bundle groups, theassignment being based on an associated fuel bundle characteristic. Forexample, the fuel bundle characteristic may be an exposurecharacteristic.

In another embodiment of the present invention, one of a plurality ofbundle groups is selected. A grouping operation is performed on theselected bundle group.

In another example embodiment of the present invention, a plurality offuel bundle groups in a current loading map is created. A firstplurality of proposed loading maps is generated to establish potentialcore loading at a next cycle of operation. The plurality of proposedloading maps are filtered to create a second plurality of proposedloading maps, the second plurality of proposed loading maps satisfyingat least one fuel bundle group constraint. An objective function isconfigured to evaluate the second plurality of proposed loading maps.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given herein below and the accompanying drawings,wherein like elements are represented by like reference numerals, whichare given by way of illustration only and thus are not limiting on thepresent invention and wherein:

FIG. 1 illustrates an embodiment of an architecture according to thepresent invention; and

FIG. 2 illustrates a screen shot of a partially completed templatedesigned according to the methodologies of the present invention usingthe loading map editor of the present invention;

FIG. 3 illustrates a reload window displayed by a loading map editor ofthe present invention;

FIG. 4 illustrates a filter window displayed by a loading map editor ofthe present invention; and

FIG. 5 illustrates a load fresh window displayed by a loading map editorof the present invention.

FIG. 6 illustrates a flow chart of a process for creating bundle groups.

FIG. 7 illustrates a screen shot of a portion of the available fuelbundle positions within a loading map according to the methodologies ofthe present invention.

FIG. 8 illustrates a screen shot of a Wizard window according to themethodologies of the present invention.

FIG. 9 illustrates a screen shot of a list of available IAT types for aselected fresh bundle group.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

To better understand the present invention, an example method ofcreating a template and loading map will be described. Then, a processof generating bundle groups within a loading map will be described.Finally, example implementations of bundle groups being used as aconstraint during an optimization process will be given.

A Generic Architecture

FIG. 1 illustrates an embodiment of an architecture according to thepresent invention. As shown, a server 10 includes a graphical userinterface 12 connected to a processor 14. The processor 14 is connectedto a memory 16. The server 10 is directly accessible by a user inputdevice 18 (e.g., a display, keyboard and mouse). The server 10 is alsoaccessible by computers 22 and 26 over an intranet 20 and the Internet24, respectively. The operation of the architecture shown in FIG. 1 willbe discussed in detail below.

Creating a Template

A user via input 18, computer 26 or computer 22 accesses the server 10over the graphical user interface 12, and runs a loading map editorprogram stored in memory 16 according to an exemplary embodiment of thepresent invention. The loading map editor provides for creating andediting a graphical representation of a nuclear reactor core referred toas a template. However, another form of conveying this information, suchas a text file, may also be thought of as the template. FIG. 2illustrates a quarter-core screen shot of a partially completed templatedesigned according to the methodologies of the present invention usingthe loading map editor of the present invention.

When the loading map editor is initially run, the user has the optionvia a file menu 30 to access a previously created template or to begin anew template. Assuming the user begins a new template, the loading mapeditor requests the user to identify the nuclear reactor for which thetemplate is being created. The loading map editor then retrieves thegeometry of the identified nuclear reactor from a relational databasecontaining nuclear reactor plant characteristics stored in the memory18. The loading map editor then displays a blank colorless fuel bundlefield 36 of the appropriate size based on the retrieved plantcharacteristics with the rows and columns numbered (such as with thefuel bundle position Row 6, Column 3 in FIG. 2).

Within the fuel bundle field 36, the user may then, for example, using amouse associated with the input 18, computer 26 or computer 22 click onthe fuel bundle positions 38 in the array of possible fuel bundlepositions to identify the type (fresh, reinsert, or locked) and settingof the actual fuel bundle in that position. The user may then assignfuel bundles to one of a plurality of fuel bundle sets. Examples ofcriteria upon which a user may select the bundle set assignment will bedescribed later.

As shown on the right side of FIG. 2, the loading map editor providesseveral tools for performing this assignment task. Specifically, thetools include the headings Load type 40, Bundle Setting 50 and NumberingMode 60.

An example bundle set selection will now be described. Under the LoadType 40 tool heading, the loading map editor includes a Fresh radiobutton 42, a Reinsert radio button 44 and a Locked radio button 46. TheFresh, Reinsert and Locked radio buttons 42, 44 and 46 correspond tofresh, reinsert and locked fuel bundle categories. The user, forexample, clicks on the desired radio button to choose the desiredcategory and then clicks on the fuel bundle position 38 in the fuelbundle field 36 to assign that category to the fuel bundle position 38.The fresh fuel bundle category indicates to insert fuel bundles thathave not been exposed. The loading map editor then displays “F” and anumber “N” at the bottom of the fuel bundle position 38. The “F”indicates the fresh fuel bundle category, and the number “N” indicatesthe Nth fresh bundle type 38. As will be appreciated, the loading mapeditor maintains a count of the number of fuel bundle types assigned tothe core. Multiple bundle positions can be assigned the same bundle typeby specifying the same “F” and “N” value for each position.

The locked fuel bundle category indicates that a fuel bundle currentlyoccupying an associated fuel bundle position in an actual nuclearreactor core is to remain in that position in creating a new nuclearreactor core loading map. The loading map editor displays “L” and anumber “N” in the fuel bundle position 38 when the locked fuel bundlecategory is assigned. The “L” indicates the locked fuel bundle category,and the number “N” indicates the Nth locked bundle set.

The reinsert fuel bundle category indicates to insert a fuel bundle thathas been exposed. The loading map editor displays only a number “N” inthe fuel bundle position 38 when the reinsert fuel bundle category isassigned. The number indicates a priority of the fuel bundle position38. The number and the priority indicated by the number will bedescribed in detail below with respect to the Numbering Mode 60 heading.

In an exemplary embodiment, the loading map editor displays the fuelbundle positions 38 in a color associated with the assigned category.For example, fresh are displayed in blue, locked are displayed inyellow, and reinserted are displayed in violet.

Under the Bundle Setting 50 heading, the loading map editor includes a“1” radio button, a “2” radio button, a “4” radio button, and an “8”radio button. When the “1” radio button is selected by the user, forexample, by clicking on the “1” radio button, the category assigned bythe user to a fuel bundle position 38 is associated only with the fuelbundle position 38 chosen. Selecting the “2” radio button and assigninga category to a fuel bundle position 38 causes the category to beassigned to the selected fuel bundle position as well as the fuel bundleposition 180 degrees symmetric to the selected fuel bundle position.Selecting the “4” radio button causes the loading map editor to requestthe user to choose between rotational and mirror symmetry. Rotationalsymmetry is an image property indicating there is a center point aroundwhich the object is turned a certain number of degrees and the objectstill looks the same (i.e., it matches itself a number of times while itis being rotated,). Mirror symmetry (or line symmetry) indicates acorrespondence in size, shape, and relative position of parts onopposite sides of a dividing line. If the user assigns a category to afuel bundle position when rotational symmetry is chosen, this causes thecategory to be assigned to the selected fuel bundle position as well asthe fuel bundle position 38 in each of the other quadrants rotationallysymmetric to the selected fuel bundle position. If the user assigns acategory to a fuel bundle position when mirror symmetry is chosen, thiscauses the category to be assigned to the selected fuel bundle positionas well as the fuel bundle position in each of the other quadrantssymmetric to the selected fuel bundle position.

Selecting the “8” radio button causes the loading map editor to considerthe total fuel bundle field 36 as octant symmetric—eight symmetric piepieces. Assigning a category to a fuel bundle position when the “8”radio button is selected causes the category to be assigned to theselected fuel bundle position 38 as well as the fuel bundle positions 38in each of the other eight pie pieces symmetric to the selected fuelbundle position 38.

Under the Numbering Mode 60 heading, the loading map editor includes anAutomatic radio button 62 and a Manual radio button 64. Choosing betweenan automatic numbering mode by selecting the Automatic radio button 62and a manual numbering mode by selecting the Manual radio button 64 isonly permitted when the Reinsert radio button 44 or Fresh radio button42 has been selected. The numbering mode in general is inapplicable whenthe Locked radio button 46 is selected.

When the Automatic radio button 62 is selected, the loading map editor,which maintains a count of the number of fuel bundle positions 38assigned the reinsert fuel bundle category, assigns the count plus oneto the next fuel bundle position 38 assigned the reinsert fuel bundlecategory. The assigned number is displayed at the bottom of the fuelbundle position 38. Likewise, the loading map editor maintains a countof the fresh bundle types. When a fuel bundle position 38 is assignedthe fresh bundle category the count plus one, referred to above as N, isassigned to that position. “F” and the value of N are displayed at thebottom of the fresh fuel bundle position.

When the Manual radio button 64 is selected, the loading map editormaintains the count of the number of fuel bundle positions 38 assignedthe reinsert fuel bundle category, but does not assign numbers to thefuel bundle positions 38. Instead, the user may position a cursor in thefuel bundle position 38 and enter the number manually. As alluded toabove, the assigned numbers represent assigned priorities. Thepriorities indicate an order for loading exposed fuel bundles based onan attribute of the exposed fuel bundles. The attributes include, butare not limited to, K infinity (which is a well-known measure of theenergy content of the fuel bundle), exposure of the bundle (which isaccumulated mega-watt days per metric ton of uranium in the bundle),residence time of the bundle (which is how long the bundle has beenresident in the nuclear reactor core), etc. In one exemplary embodiment,the shade of the color associated with the reinserted fuel bundlepositions varies (lighter or darker) in association with the assignedpriority.

The loading map editor according to the present invention also providesseveral viewing options via a view menu 34 and a zoom slide button 70.Adjusting the zoom slide button 70 by clicking and dragging the zoomslide button 70 to the left and the right decreases and increases thesize of the displayed fuel bundle field 36. Under the view menu 34, theuser has the option to view a single quadrant of the template, or a fullcore view of the template. Additionally, the user can control whethercertain template attributes are displayed. Specifically, the view menu34 includes the options of displaying the following in the loadingtemplate: control blades, bundle coordinates, core coordinates, etc.

Having created the loading template, the user may save the template, oreven a partially created template, to the memory 18 by selecting eitherthe “Save” or “Save As” option in the file menu 30.

As discussed above, instead of creating a new template, a previouslycreated template may be viewed and, optionally, edited. Using the filemenu 30, the user selects an “open” option. The loading map editor thendisplays the accessible templates stored in the memory 18 or a directoryof memory 18. The user then selects an accessible template, for example,by clicking on one of the accessible templates. The loading map editorwill then display the chosen template.

The user may then edit the chosen template. For example, after selectinga fuel bundle position 38 the user may select under the edit menu to“clear” the category assigned to the fuel bundle position 38. Besidesthe category assigned to this fuel bundle position 38, the loading mapeditor also clears the category assigned to associated fuel bundlepositions 38. Associated fuel bundle positions 38 are those fuel bundlepositions 38 that were assigned the fuel bundle category along with thefuel bundle position 38 selected for clearing because of the bundlesetting chosen when the category was assigned to the fuel bundleposition 38 chosen for clearing.

When fuel bundle positions 38 assigned the fresh or reinserted categoryare cleared, the loading map editor adjusts the numbering associatedwith that category. In the case of the fresh bundle category, this is aconditional action based on whether other bundle positions have beenassigned the same fresh bundle type. Specifically, the loading mapeditor performs a cascade operation such that fuel bundle positionsassigned the same category and having higher numbers are renumbered insequence beginning from the lowest number of a deleted fuel bundleposition. For example, if reinsert bundle positions numbered 44, 43 and42 were cleared, then reinsert bundle position having number 45 would berenumbered 42, reinsert bundle position having number 46 would berenumbered 43, etc. The loading map editor also changes the total countof fuel bundle positions assigned the category being cleared.

When unassigned bundle positions are created through editing, the usermay then newly assign categories to the unassigned bundle positions inthe same manner and using the same tools to create a template asdescribed above. In so doing, the user may decide to manually assign,for example, an existing priority to a newly assigned reinsert fuelbundle position. In this instance, the reinsert fuel bundle positionalready having this number and each reinsert fuel bundle position havinga higher number are incremented by one.

As a further alternative, the user may want to adapt an existingtemplate for one reactor to another reactor of the same size andphysical bundle configuration. To do this, the user may use the “saveas” feature in the file menu 30 to create a duplicate of the loadingtemplate. Subsequent changes to the bundle field will then apply to thecopied template.

In addition to creating a template from ‘scratch’ or editing an existingtemplate, the user may have the loading map editor derive a templatefrom a previously loaded core. In the loading map editor, using the filemenu 30, the user selects an “auto-generate template” option. Theloading map editor then displays a list of the accessible fuel cyclesstored in the memory 18. Each fuel cycle corresponds to an actualloading map for a fuel cycle of a nuclear reactor. As will beappreciated, the memory 18 may store loading maps for cycles ofdifferent nuclear reactors. Accordingly, the list of cycles displayed bythe loading map editor identifies both the nuclear reactor and thecycle. From the list the user selects the cycle (hereinafter “theselected cycle”) that the template will be derived from. The loading mapeditor then accesses the loading map for the selected cycle.

The user is then presented with a dialog box for entering inputparameters of the derivation process. The input parameters include: aprimary attribute (e.g., exposure, K infinity, etc.) for deriving thetemplate, a tolerance level (discussed in detail below), set listmembers (8, 4, or 2 bundle settings), bundle symmetry for sets of 4, anda maximum number of assignments to each set list member. For example theuser may enter K infinity as the primary attribute, and a tolerancelevel of 0.2 (which, as described in detail below, is used for formingbundle sets). The user may further enter that sets of 8 and 4 arepermitted, the sets of 4 should have mirror symmetry and that a maximumof 14 sets of 4 are permitted. In an exemplary embodiment, the loadingmap editor provides the user with a drop-down menu. The user selectslist members desired for the template from the options given in thedrop-down menu. These options include: sets of 8, 4 and 2; sets of 8 and4; sets of 8 (which forces sets of 4 on the minor axis of the reactorcore template); and sets of 4 and 2. In selecting the maximum number ofassignments for each set, the user enters this data in the order of thesmallest to the largest set size. However, the maximum number ofassignments for the largest sets is not entered by the user, as thisvalue is automatically determined based on the maximum number ofassignments for the smaller sets.

Once the user enters the input parameters, the loading map editor willbegin generating a template.

First the loading map editor asks the user if locked bundle positionsare permitted, if so, then the loading map editor requests the user toidentify the cycle previous to the selected cycle in the same mannerthat the selected cycle was identified. The loading map editor thencompares the loading map for the selected cycle with the loading map forthe previous cycle of the identified nuclear reactor. Specifically, foreach bundle position in the reactor, the loading map editor determinesif loading maps for the selected and previous cycles have a bundle withthe same serial number in the same bundle position. If so, the bundleposition is assigned the locked fuel bundle category in the loadingtemplate.

After the locked fuel bundle positions are identified, the loading mapeditor identifies the fresh fuel bundle positions. Specifically, foreach bundle position not already identified as a locked bundle position,the loading map editor determines from the characteristics of theselected loading map if the fuel bundle in that bundle position is afresh fuel bundle. For each identified fresh fuel bundle, the loadingmap editor also determines the type of fresh fuel bundle from thecharacteristics of the selected loading map. The loading map editor thenassigns the fresh fuel category to the associated fuel bundle positionin the template and assigns a type count number N to the fuel bundleposition. For each type of fresh fuel bundle located in the selectedloading map, the loading map editor assigns a count value to that type.This count value is then assigned to the bundle position along with thefresh fuel bundle category assignment so that fresh fuel bundlepositions that should have the same type of fresh fuel bundle areidentified by the same value ‘N’ in the loading template.

Next, the loading map editor determines whether the identified freshbundle category positions form any bundle sets. As discussed above, theuser identifies the bundle set members permitted in the template. Thebundle set members form a set members list. For each bundle positionassigned the fresh fuel bundle category, the loading map editor firstdetermines if the bundle position (hereinafter the “current bundleposition”) has already been assigned to a set. If so, then the loadingmap editor proceeds to the next bundle position. If not, then theloading map editor selects the largest set from the set member list andidentifies each of the bundle positions that form such a set with thecurrent bundle position. If each of the bundles positions forming theset has been assigned the fresh bundle category and are of the same typeas the current bundle position, then the loading map editor records theset of bundle positions as a set. If each of the bundle positionsforming the set has not been assigned the fresh bundle category or oneof the bundles is not the same type as the current bundle position, thenthe loading map editor performs the above-described process for the nextlargest bundle set in the set member list. This process keeps repeatinguntil a set is formed or there are no more sets in the set member listto test. If the members of the set member list have been tested, and noset has been formed, then the current bundle position is recorded as notbelonging to a set.

Next, the loading map editor identifies the reinserted fuel bundlepositions. The bundle positions of the template not assigned to thelocked or fresh fuel bundle categories are assigned the reinserted fuelbundle category. Then, the loading map editor determines whether thereinserted bundle category positions form any bundle sets. For eachbundle position assigned the reinserted fuel bundle category, theloading map editor first determines if the bundle position (hereinafterthe “current bundle position”) has already been assigned to a set. Ifso, then the loading map editor proceeds to the next bundle position. Ifnot, then the loading map editor selects the largest set from the setmember list and identifies each of the bundle positions that form theset with the current bundle position. If each of the bundles positionsforming the set has not been assigned the reinserted bundle category,then the loading map editor determines if the next largest set in theset member list includes all reinserted fuel bundle positions. If no setfrom the set member list results in a set of reinserted fuel bundles,then the loading map editor records the current fuel bundle position asnot belonging to a set.

Once a set has been formed, the loading map editor calculates theaverage attribute value for the set. As discussed above, the useridentified a primary attribute to use in deriving the template. Here,the loading map editor uses that attribute value for each fuel bundle inthe selected loading map forming the associated set in the template tocalculate the average attribute value. The loading map editor thendetermines if the attribute value for each fuel bundle in the set iswith the tolerance level from the average attribute. Again, here, thetolerance level was a user input design parameter as discussed above.

If the attribute value for each fuel bundle in the set is within thetolerance level of the average attribute value, then the loading mapeditor records the associated fuel bundle positions in the template asbelonging to a set. Otherwise, the loading map editor performs theabove-described process for the next largest bundle set in the setmember list. This process keeps repeating until a set is formed or thereare no more sets in the set member list to test. If the members of theset member list have been tested, and no set has been formed, then thecurrent bundle position is recorded as not belonging to a set.

The loading map editor then determines if the user specified maximum fora set in the set member list has been violated. If so the editorperforms a set recombination and ranking process. For example, if thenumber of sets of 2 exceeds the user specified maximum the editor doesthe following: For each set of 2, the loading map editor determines ifanother set of 2 forms a set of 4 meeting the symmetry requirementsentered by the user. The loading map editor then determines the averageattribute value and standard deviation for each newly formed potentialset of 4 and ranks the potential sets of 4 based on minimum standarddeviation. Next, the highest ranked sets (i.e., those with the loweststandard deviation) are assigned to the sets of 4 until the sets of 2list does not exceed the maximum number allowed based on the user input.Those potential sets of 4 not assigned remain as sets of two. Next, thesame process is performed to combine sets of 4 into sets of 8 assumingthe user input parameters permit sets of 8 and the user specifiedmaximum for sets of 4 has been violated.

As a final step, the reinserted fuel bundles are assigned a prioritynumber that, as described above, appears in the template. The fuelbundles positions are ranked based on (1) the attribute value for thefuel bundle in the associated position in the loading map if the fuelbundle position does not form part of a set; or (2) by the averageattribute value of the set if fuel bundle position does form part of aset. A priority number is then assigned by this ranking with the fuelbundles having the same average attribute assigned the same prioritynumber.

This completes the template derivation process, the resulting templateis then displayed in the loading map editor allowing the user to savethe resulting template for future use.

Using the present invention as described above, a core designer maycapture his experience and rules of thumb associated with the initialdesign of a loading map. Furthermore, this knowledge may then be used byothers to improve or adapt templates to existing core designs.

Creating Loading Map

The loading map editor according to the present invention includesadditional functionality that allows the user to generate a loading mapfrom the loading template. In addition, the loading map editor providesincreased flexibility in creating the loading map by allowing the userthe option of reloading fuel bundles currently residing in one or morefuel pools.

After accessing, creating and/or editing a reactor core template usingthe loading map editor as discussed above, the user may then create aloading map using the template. From the file menu 30, the user choosesa “load” option. The loading map editor then displays a loading screenthat includes a template access window, template information window,reload window and a load fresh window. The template access windowprovides a user with a drop down menu for selecting a loading templatestored in the memory 18. The template information window displayssummary information for the selected loading template. The summaryinformation includes, but is not limited to, the number of fresh bundletypes, the number of reinserted fuel bundle positions and the number oflocked bundle positions in the loading template. The summary informationmay also indicate the number of fresh bundle types and number ofreinserted bundles currently added in creating the loading map.

FIG. 3 illustrates an exemplary embodiment of a reload window displayedby the loading map editor. The window is divided into two parts: afiltered fuel pool table 100 and a reloading pool 200. The filtered fuelpool table 100 lists (1) the exposed fuel bundles currently in thenuclear reactor under consideration, except for those fuel bundles inlocked fuel bundle positions 38, and (2) the fuel bundles in one or morefuel pools for this and other nuclear reactors. As is well-known,exposed fuel bundles removed from a nuclear reactor are stored in whatis known as a fuel pool. Fuel bundles from two or more nuclear reactorcores located at a same site may be stored in the same fuel pool.

As shown in FIG. 3, the filtered fuel pool table 100 lists each exposedfuel bundle by its serial number and bundle name. Each fuel bundle isassigned a unique serial number, used to assure traceability of thebundle from a quality assurance perspective. The bundle name is acharacter string identifier used to identify the fuel bundle productline as well as nuclear characteristics, such as uranium and gadolinialoading. The filtered fuel pool table 100 also lists one or moreattributes of each exposed fuel bundle listed. These attributes mayinclude K infinity, exposure, and the last fuel cycle number for whichthe bundle was resident in the core. Additional attributes for anexposed fuel bundle may include: 1) bundle product line, 2) initialuranium loading, 3) initial gadolinium loading, 4) number of axialzones, 5) historical fuel cycle numbers previous to the most recent forwhich the bundle was resident in the core, 6) the corresponding reactorin which the fuel bundle was resident for each of the historical fuelcycles, 7) accumulated residence time, and 8) fuel bundle pedigree, aparameter that reflects the usability of the bundle for continuedreactor operation.

The fuel bundle pedigree is determined from a number of factors theforemost being an inspection of the fuel, either visually or by someother non-destructive test procedure, which is designed to detect acurrent failed fuel bundle or the vulnerability of the bundle to futurefailure. Failure mechanisms include such items as corrosion, debrisimpact, and mechanical bowing of the fuel bundle. Another factoraffecting pedigree is possible reconstitution of a fuel bundle, which isa repair process involving the replacement of damaged fuel rods withreplacement rods that may be a uranium containing fuel rod oralternatively, a non-uranium containing rod (e.g. stainless steel),henceforth referred to as a ‘phantom’ rod. A pedigree attribute might be‘RU’ and ‘RP’ for reconstituted with uranium and phantom rods,respectively, and ‘DC’, ‘DD’ and ‘DB’ for damaged by corrosion, debris,and bow, respectively. A ‘blank’ pedigree attribute would designate abundle that was undamaged and useable.

All attributes with the exception of bundle pedigree are populatedwithin the database via a direct relationship with the historical fuelcycles. The fuel pedigree attribute for non ‘blank’ designations areentered into the database via a separate process that is tied to fuelinspection and reconstitution services. In this process, the fuelbundles in a fuel pool are inspected and the pedigrees of the fuelbundles ascertained from the inspection. Then, a bundle status programis accessed. The bundle status program provides a GUI menu for ‘FuelInspection’, which is accessed by the user. The user clicks on thepulldown menu ‘Add’ from the ‘Fuel Inspection’ menu, and is presentedwith a pop-up for typing in the bundle serial number and the pedigreedesignation, such as ‘DD’ corresponding to a debris damaged bundle. Thepedigree data entered in this manner is associated with the fuel pooldatabase. The user may also click a ‘Census’ option from the ‘FuelInspection’ menu. Selecting this option will perform a query of the fuelpool database and present the user with a list of bundle serial numbersand corresponding attribute data, as described previously, for thosebundles containing a non-null pedigree designation. The user may electto change existing pedigree information by selecting the bundle entry,right-clicking a ‘Modify’ option, which activates the pedigree attributefield, and entering the modified pedigree information. For example, abundle that was previously damaged may have been reconstituted.Alternatively, the user may right-click a ‘Delete’ option, which has theeffect of reverting the bundle pedigree status back to null.

The reloading fuel pool table 200 provides the same information for eachfuel bundle as provided by the filtered fuel pool table 100.Additionally, the reloading fuel pool table 200 indicates the prioritynumber 202 for each fuel bundle set as set forth in the loadingtemplate. As discussed above with respect to the loading template,reinserted fuel bundles may be assigned as a set of 1, 2, 4 or 8bundles. Accordingly, FIG. 3 shows that the highest priority reinsertedfuel bundle position(s) are a set of four fuel bundles, and the nexthighest priority reinserted fuel bundle(s) are a set of eight fuelbundles.

The reloading fuel pool table 200 is populated by moving fuel bundlesfrom the filtered fuel pool table 100 into the reloading fuel pool table200. As further shown in FIG. 3, the reload window further includes aset of tools 120 for aiding the user in selecting and moving fuelbundles from the filtered fuel pool table 100 to the reload fuel pooltable 200. The set of tools 120 include, but are not limited to, afilter tool 130, a move right tool 160, a move left tool 170 and adelete tool 180.

A user selects the filter tool 130 by, for example, clicking on thefilter tool 130. This opens a filter window as shown in FIG. 4. Asshown, the filter window lists the same attributes listed in thefiltered fuel pool table 100, and allows the user to indicate to filterbased on the attribute by clicking in the selection box 132 associatedwith the attribute. When an attribute has been selected, a check isdisplayed in the associated selection box 132. The user may alsounselect an attribute by again clicking in the associated selection box.In this case, the check mark will be removed.

For each attribute, the filter window may display one or more filtercharacteristics associated with the attribute. For example, for thefilter characteristics of the K infinity attribute, the user may selecta filter operator 134 of greater than, less than, or equal to and enterin a filter amount 136 associated with the filter operator 134. As shownin FIG. 4, a user has selected to filter based on K infinity, chosen thegreater than filter operator, and entered the filter amount of 1.2. As aresult, the loading map editor will filter the fuel bundles in thefiltered fuel pool table 100 to display only those fuel bundles having aK infinity greater than 1.2. As another example, the exposure attributealso has an associated filter operator and filter amount.

As will be appreciated, the filter characteristics of an attribute willdepend on the attribute. Also, as will be appreciated, othermethodologies for indicating the filter characteristics may be possible.For example, for the cycle attribute, the filter window provides a dropdown menu for selecting the cycle number. FIG. 4 shows cycles 2 and 4selected from the drop down menu for the cycle attribute. As a result,the loading map editor filters the filtered fuel pool table 100 todisplay only those fuel bundles whose most recent residence was in cycle2 or cycle 4. Similarly, the user may elect to filter bundles based ontheir pedigree, product line, etc. Once the attributes for filtering onhave been selected and the filter characteristics have been entered, theuser causes the loading map editor to filter the filtered fuel pooltable based on this information by clicking on the OK selection box.Alternatively, the user may cancel the filter operation by clicking onthe CANCEL selection box.

The filtered fuel pool table 100 also provides a filtering mechanism forfiltering the fuel bundles listed therein. A user may sort the filteredfuel pool table 100 in ascending or descending order of an attribute byclicking on the attribute heading in the filtered fuel pool table 100.Once the user clicks on the attribute, the loading map editor displays apopup menu with the options “Sort Ascending” and “Sort Descending”. Thefiltered fuel pool table 100 is then filtered in ascending or descendingorder of the attribute based on the option clicked on by the user.

To move fuel bundles from the filtered fuel pool table 100 to the reloadfuel pool table 200, the user selects the fuel bundles for transfer byclicking and dragging to highlight one or more of the fuel bundles inthe filtered fuel pool table 100. Then the user clicks on the move righttool 160. This causes the selected fuel bundles to populate the highestpriority unpopulated fuel bundle positions in the reload fuel pool table200. Alternatively, a user clicks and drags the highlighted fuel bundlesinto one of the priority sections of the reloading fuel pool table 200.

Fuel bundles may also be moved from the reload fuel pool table 200 backinto the filtered fuel pool table 100 by selecting fuel bundles in thereload fuel pool table 200 and clicking on the move left tool 170.Alternatively, the selected fuel bundles may be clicked and dragged backto the filtered fuel pool table 100.

The delete tool 180 provides the user with the function of deleting fuelbundles from either the filtered or reload fuel pool tables 100 and 200.The user may select one or more fuel bundles in one of the tables, andclick the delete tool to delete the selected fuel bundles from thetable.

Next, the loading of fresh bundles into the template will be described.FIG. 5 illustrates an exemplary embodiment of a load fresh windowdisplayed by the loading map editor. The window is divided into twoparts: a fresh bundle types table 300 and a fresh bundle pool table 400.The fresh bundle types table 300 lists the available fresh fuel bundletypes.

As shown in FIG. 5, the fresh bundle types table 300 lists each freshfuel bundle type by its bundle name. The bundle name is a characterstring identifier used to identify the fuel bundle product line as wellas nuclear characteristics, such as uranium and gadolinia loading. Thefresh fuel bundle types table 300 also lists one or more attributes ofeach fresh fuel bundle type listed. These attributes may include Kinfinity, fuel bundle product line, average uranium-235 enrichment,percent (as a function of total fuel weight) of gadolinia burnablepoison contained in the fuel bundle, number of gadolinia-containing fuelrods, and number of axial zones, where an axial zone is defined by across-sectional slice of the bundle that is homogeneous along the axialdirection. Other attributes of the fresh bundle may include parametersfor predicted thermal behavior, such as R-factors and local peaking,calculated for various bundle exposure values. R-factors are used asinputs to the critical power ratio (CPR) and are determined from aweighted axial integration of fuel rod powers. Local peaking is ameasure of the fuel rod peak pellet and clad temperature.

The fresh bundle pool table 400 provides the same information for eachfuel bundle as provided by the fresh bundle types table 300.Additionally, the fresh bundle pool table 400 indicates the type number402 for each type of fresh bundle in the loading template and thennumber of fresh fuel bundles of that type in the loading template. FIG.5 shows that the first type of fresh fuel bundle position(s) are a setof four fuel bundles, and the next type of fresh fuel bundle(s) are aset of eight fuel bundles.

The fresh bundle pool table 400 is populated by moving fuel bundles fromthe fresh bundle types table 300 into the fresh bundle pool table 400.As further shown in FIG. 5, the load fresh window includes the samefilter tool 130, move right tool 160 and delete tool 180 for aiding theuser in selecting and moving fuel bundles from the fresh bundle typestable 300 to the fresh bundle pool table 400 as already described above.As will be appreciated, because the attributes for the fresh fuelbundles are different than the reinserted fuel bundles the filteringcharacteristics may also differ accordingly. The loading map editor alsoprovides, as shown in FIG. 5, for filtering the fresh bundle types table300 in ascending or descending order of an attribute in the same mannerthat the filtered fuel pool table 100 may be sorted.

The selection and moving process for fresh fuel bundles does differ fromthe process for moving burnt fuel because the destination of the fuelmust be chosen in the set fresh fuel bundle pool table 400 located onthe right side of the fresh bundle types table 300. Namely, after a userselects the fresh bundle type from the fresh bundle types table 300, theuser then selects one or more fuel bundle positions in the fresh fuelbundle pool table 400. By selecting the move right tool 160, theselected fuel bundle positions in the fresh fuel bundle pool table 400are populated with the selected fresh bundle type. Alternatively, theuser may click and drag the bundle type into the fresh fuel bundle pooltable 400. Unlike with the filtered fuel pool table 100, the fresh fueltypes are not removed from the fresh bundle types table 300 but are,instead, copied as fuel bundles into the fresh bundle pool table 400.

Once the reinserted and fresh fuel bundle positions 38 are filled usingthe tools described in detail above, the user may click on a “Load”button 184 displayed in the loading screen. This step performs theassignment of the fresh and reinserted fuel bundles from the freshbundle pool list 400 and reloading pool 200, respectively, to thephysical I,J locations in the core loading map. The core loading map isthen displayed to the user as shown in FIG. 7. The user may then savethe created loading map by choosing “Save” or “Save As” from the OptionsMenu 760 within FIG. 7.

Further refinement of the core loading map may be performed. The userhas the option of performing a “swap” or exchange of two bundles, whichmay be between either fresh or reinserted bundles. The user enters“Shuffle” by clicking on a “shuffle” radio button 707 under “Mode”. Theuser then selects a symmetry 710 followed by selection of a first andsecond location within the core loading map. All symmetric partners ofthe first location will exchange with all symmetric partners of thesecond location. While in shuffle mode, this process may be repeated toperform any number of rearrangements of fresh and reinserted fuel withinthe core loading map.

A second refinement to the core loading map involving a change in thefresh fuel bundle design (i.e. a change in fresh fuel type or IAT, anumber assigned to a specific fuel bundle design within the loading map)may be performed. The user enters “IAT” mode by clicking on a “IAT”radio button 709. The IAT is a designation of a fuel bundle type (e.g.,IAT 1, IAT 2, etc. . . . ). For example, a given IAT number may bereserved for fresh fuel bundles. The user selects a symmetry and thenclicks on a fresh location in the core loading map. A pop-up windowappears with an IAT pull-down, from which the user selects a new IAT forthe targeted location (along with the symmetric partners of the targetedlocation). While in IAT mode, the process of changing fresh bundle typeswithin fresh core locations may be repeated any number of times.

Having created the loading map, the user may then perform simulations onreactor core performance, etc. using the loading map created accordingto the methodologies of the present invention. The “Shuffle” and “IAT”modes for refining the loading map may be performed iteratively with thesimulating step, with the results from the simulation being used as aguide to facilitate improvement to the core loading map.

By allowing the user to draw on the resources of the fuel pool(s), thepresent invention provides for greater flexibility in the creation ofthe loading map and may also reduce the overall cost in loading anuclear reactor core.

Creating Bundle Groups

Once a loading map has been generated (e.g., with the above describedmethodology), a core designer may assign fuel bundles into one of aplurality of bundle groups. The bundle groups are generated withattributes that define the bundle group.

FIG. 6 illustrates a flow chart of a process for creating bundle groups.Referring to FIG. 6, in step S600, a core designer enters a group modewithin an input deck of a loading map editor. This step will bedescribed with reference to FIG. 7. FIG. 7 illustrates a screen shot ofa portion of the fuel bundles within a loading map according to themethodologies of the present invention. As shown, the loading mapincludes a plurality of fuel bundles 720. The position of the fuelbundles 720 as viewed in the loading map relates to the position of thefuel bundles 720 in the core. Further, each of the fuel bundles 720includes displayed data associated with the fuel bundles 720. Forexample, as shown in FIG. 7, the displayed data includes a bundle groupnumber (in the top left portion of fuel bundles 720 associated with agiven bundle group), bundled average K infinity (K-inf) (not shown)(e.g., in the center portion of fuel bundles 720), and the exposure inGigaWatt Days/short ton (GWD/st) (not shown) (e.g., in the bottomportion of fuel bundles 720).

As shown, a core designer utilizing the above-described loading mapeditor enters a Group Mode by selecting a tab “Bundle Groups” 700 from aplurality of tabs 703. Then, the core designer selects group mode 705from a plurality of mode options (e.g., group 705, shuffle 707, IAT709).

Referring to FIG. 6, in step S605, the core designer determines whetherto execute a grouping operation manually or with a Wizard. The Wizard isa software tool which may be used to automate bundle group generation.If the core designer decides to execute the grouping operation manually,the core designer may assign fuel bundles to bundle groups through abundle by bundle, iterative process and the process advances to stepS610. In this embodiment, the core designer analyzes each fuel bundleindividually and determines to which bundle group the fuel bundle underconsideration is to be assigned based on at least one of a plurality ofattributes. The criteria the core designer may consider when generatingor editing bundle groups will be described later.

In step S610, the core designer chooses between performing a groupingoperation on an existing bundle group (or individual fuel bundlebelonging to a bundle group) or perform a grouping operation on anexisting bundle group, then in step S613, the core designer selects abundle group on which to execute a grouping operation. The core designerleft clicks a fuel bundle belonging to the selected bundle group.Referring again to FIG. 7, fuel bundles 720 represent a sample of theavailable fuel bundles which the core designer may click to designate abundle group. Fuel bundles 722 represent fuel bundles belonging to abundle group selected by the core designer. As shown, the selected fuelbundles 722 are highlighted and each belong to the same group (i.e.,group “1”). The group number for group “1” is displayed by groupdesignation number 724. Group designation number assignment will bedescribed later. Thus, group “1” is set to an active state, which meansthat grouping operations will affect group “1” until the core designersets another group to the active state.

Then, in step S615, the core designer right clicks on a selected fuelbundle and a list of available grouping operations associated with thefuel bundle become available. If the selected fuel bundle belongs to agroup, the available grouping operations include 1) Remove Bundles FromGroup and 2) Delete Group. If the selected fuel bundle does not belongto a group, the available grouping operations only 3) Add Bundles toGroup. The grouping operation of 4) Create Group is not available hereand will be described later with respect to steps proceeding from stepS635.

The core designer selects one of the available grouping operations andleft clicks the selected operation with the mouse. If 1) Remove BundlesFrom Group is clicked, the process advances to step S620. If 2) AddBundles To Group is clicked, the process advances to step S625. If 3)Delete Group is clicked, the process advances to step S630.

In step S620, the selected fuel bundle and its symmetric partners (e.g.,the fuel bundles associated with the selected fuel bundles based on thesymmetry being 1, 2, 4M, 4R, 8, etc.) are removed from their bundlegroup and reset to a status of not belonging to a group. Thus, the groupdesignation number in the upper left portion of the fuel bundle isremoved. The process may then advance to step S655.

In step S625, the selected fuel bundle and its symmetric partners areadded to the group selected in step S613. The group designation numberin the upper left portion of the selected fuel bundle and its symmetricpartners is set to match the group designation number of the selectedgroup. The process may then advance to step S655.

In step S630, the group selected in step S613 is deleted entirely. Thus,each fuel bundle in the loading map belonging to the selected group isreset to a status of not belonging to a group. The group designationnumber for each fuel bundle in the group is removed from the upper leftportion of the fuel bundle. The process may then advance to step S655.

In step S655, the execution of the grouping operation is completed. Ifanother grouping operation is required, the process advances back tostep S605. If another grouping operation is not required, the processadvances to step S680. In step S680, no additional steps are requiredand all operations required by the core designer are complete. The coredesigner may select another of the plurality of tabs to enter anotherfeature of the loading map editor or exit from the loading map editor.

Returning to step S610, if the core designer chooses to create a newbundle group, then in S635, the core designer selects a desired bundlegroup symmetry (e.g., 1, 2, 4M (Mirror), 4R (Rotational), and 8). Thecore designer left clicks the selected bundle group symmetry. Referringto FIG. 7, a symmetry 710 of 8 is selected by the core designer. Theprocess may then advance to step S640.

In step S640, the core designer selects a first fuel bundle to form thenew bundle group. In one embodiment, the core designer may left click onthe New tab. The core designer then left clicks on a fuel bundle notbelonging to a bundle group in step S650. The fuel bundle is added tothe new group and given a group designation number. The groupdesignation number is the lowest unique natural number available forgroup designation. For example, if groups “1”, “2” and “3” currentlyexist in the loading map, the new group would be designated as group“4”. In this example, the number “4” would appear in the upper leftportion of each fuel bundle assigned to group “4”. In another example,if groups “1”, “3” and “4” currently exist in the loading map, the newgroup would be designated as group “2”. In this example, the number “2”would appear in the upper left portion of the fuel bundle assigned togroup “2”.

Alternatively, in another embodiment of step S650, instead of leftclicking the New tab, the core designer right clicks a fuel bundle notbelonging to a bundle group. Available grouping operations becomeavailable to the core designer. The only available grouping operationfor the fuel bundle not belonging to a bundle group is 4) Create Group.The core designer left clicks on the 4) Create Group operation. The fuelbundle is then added to the new group as described above with respect tothe New tab embodiment.

After the first fuel bundle is assigned to the new group, the processadvances to step S645. In step S645, the core designer decides whethermore fuel bundles will be added to the newly created bundle group.

Generally, bundle groups are designated as either exposed or fresh.Fresh bundle groups include only fresh fuel bundles. Exposed bundlegroups may include fresh fuel bundles. However, in “mixed” bundlegroups, each of the included fuel bundles are treated as exposed (e.g.,with respect to swapping operations) regardless of whether the includesfuel bundles are fresh or exposed.

In one embodiment, at least three fuel bundles per symmetry section arerequired in an exposed bundle group since this is the minimum number offuel bundles required for a swapping operation only including fuelbundles within the symmetry section, which will be described later.

If the core designer chooses to add an additional fuel bundle to thenewly created bundle group, the process returns to step S650. Otherwise,the process advances to step S655.

Returning to step S605, if the core designer chooses to use the Wizard,then the core designer left clicks on the wizard button shown in FIG. 7in step S660.

FIG. 8 illustrates a screen shot of a Wizard window according to themethodologies of the present invention.

Referring to FIG. 8 with respect to step S660 of FIG. 6, when the coredesigner left clicks on the wizard button 740, a window 905 including anAdd to Group column 910, an IAT column 915, a Fresh Column 920, symmetryoptions 925, and a Create Group button 930 become available to the coredesigner. The 1) Add to Group column 910 includes input tabs and the 2)IAT and 3) Fresh columns 915/920 include indicators to the coredesigner. The 2) IAT column 915 displays all available IATs to the coredesigner. The 3) Fresh column 920 indicates whether the IAT in anassociated row is fresh. If the indicator is checked (e.g., indicator932), the IAT is fresh. If the indicator is not checked (e.g., indicator934), the IAT is not fresh.

Returning to FIG. 6, in step S665, the core designer selects a desiredbundle group symmetry (e.g., 1, 2, 4M (Mirror), 4R (Rotational), and 8)from the available symmetry options. The core designer left clicks thedesired bundle group symmetry 925 and the process advances to step S670.

In step S670, the core designer selects IAT types (i.e., bundle types)to add to the new bundle group. The core designer left clicks the inputtabs in the Add to Group Column 910 in the same row as the desired IATtype. For example, the core designer may left click on the input tab 936associated with a fresh IAT type (e.g., the fresh indicator for that rowis checked). Thereafter, only additional input tabs associated withfresh IAT types may be added to the new bundle group with the Wizard.However, either fresh or exposed fuel bundles may still added manually.Alternatively, if the core designer initially selects an input tab 938that is not associated with a fresh IAT type (e.g., the fresh indicatorfor that row is not checked), only additional input tabs not associatedwith fresh IAT types may be added to the new bundle group with theWizard. However, either fresh or exposed fuel bundles may still be addedmanually. After the core designer completes selection of IAT types to beadded to the new group, the process advances to step S675.

In step S675, the core designer clicks on the Create Group button 930within the window 905 of the Wizard tool. Each fuel bundle associatedwith the selected IAT types is added to the new group and given a groupdesignation number. If a fuel bundle associated with one of the selectedIAT types already belongs to another bundle group, the fuel bundle isremoved from the other bundle group and is added exclusively to the newgroup.

In one embodiment, if less than all of the fuel bundles of a given IATtype are desired in the new bundle group, the core designer may use theWizard to add all fuel bundles of the given IAT type to the new group.Then, the core designer may remove the fuel bundle(s) not desired in thenew group manually using above-described methods.

As discussed above, the group designation number is the lowest availableunique natural number available for group designation. For example, ifgroups “1”, “2” and “3” currently exist in the loading map, the newgroup would be designated as group “4”. In this example, the number “4”would appear in the upper left portion of each fuel bundle assigned togroup “4”. In another example, if groups “1”, “3” and “4” currentlyexist in the loading map, the new group would be designated as group“2”. In this example, the number “2” would appear in the upper leftportion of each fuel bundle assigned to group “2”. The process thenadvances to above-described step S655.

As discussed earlier, bundle groups are divided into exposed bundlegroups and fresh bundle groups. Bundles within an exposed bundle groupmay “shuffle” or be exchanged with other bundles within the same bundlegroup. In an example optimization algorithm, a minimum of three sets ofsymmetric bundles may define an exposed bundle group, the exposed bundlegroup including exposed fuel and/or fresh fuel.

In contrast to exposed bundle groups, fresh bundle groups include onlyfresh fuel. Bundles within the fresh bundle group are not exchanged orshuffled, as described above with respect to the exposed bundle group,but rather may be modified through a bundle characteristic (e.g., an IATtype) selection.

The core designer selects a list of allowable IAT types for a givenfresh bundle group from among a list of all available IAT types for thegiven fresh bundle group. While step S670 of FIG. 6 as described aboveshows how IAT types may be selected for inclusion in a new bundle group,an example will now be given where IAT types in an existing fresh bundlegroup in a current loading map may be modified.

Referring to FIG. 7, the user enters IAT Mode 709 by left ‘clicking’ onthe IAT radio button 709. The core designer then left ‘clicks’ on afresh bundle within a previously defined fresh bundle group 722 toreveal a pop-up window as shown in FIG. 9, which displays to the coredesigner a list of available IAT types 950 for the selected fresh bundlegroup 722.

Referring to FIG. 9, the core designer may select or de-select amongavailable IAT types 950 with corresponding bundle names 955 andcheckboxes 960/965. The core designer selects or de-selects an availableIAT type 950 by left clicking on the checkbox 960/965, whereincheckboxes 960 are shown de-selected and checkbox 965 is shown selected.For a current loading map, certain checkboxes 960/965 may be selectedautomatically (e.g., not by the core designer), thereby indicating IATtypes already included in the selected fresh bundle group 722. Anoptimization of the selected fresh bundle group 722 may be performed ifat least two IAT types are selected. Modifying the IAT type of a freshbundle may change the distribution of enriched uranium and gadoliniawithin the fresh bundle design.

Criteria for Bundle Group Assignment

Examples of criteria the core designer may consider in assigning fuelbundles to bundle groups will now be described.

In one example, the core designer may desire all fuel bundles withcertain IAT types to be included within a bundle group. The coredesigner may use above-described methods (e.g., manually creating thebundle groups or using the Wizard tool) to create the desired bundlegroups.

In another example, consider a situation where the core designerrequires that no fresh fuel bundles be loaded into a bundle positionadjacent to a control blade (i.e., referred to as a “controlledlocation”). In this case, the core designer creates a bundle group onlyincluding fuel bundles surrounding the controlled locations. The coredesigner further sets an attribute for the bundle group being that onlyonce burnt fuel bundles (i.e., bundles that have been in the core foronly one cycle of operation) may be loaded into the bundle group (e.g.,by adding only once burnt fuel bundles with the above-described manualprocess). During an optimization process, the core designer will onlyconsider proposed loading maps which meet the criteria established foreach of the bundle groups. Thus, the core designer uses the attributeswhich define a bundle group as a constraint, which will be discussed infurther detail below.

Bundle Groups as a Constraint in an Optimization Process

An example implementation of the assigned fuel bundle groups as aconstraint in an optimization process will now be described.

As described above, fuel bundles within a core may be assigned to one ofa plurality of bundle groups. Collectively, the fuel bundle assignmentsconstitute a loading map. During the cycle of operation in a nuclearreactor, the loading map does not change. However, a period betweencycles of operation (referred to as an “outage”), reserved for generalmaintenance of the reactor, may include a repositioning of fuel bundleswithin the core. The fuel bundles repositioned during the outage may bedesignated in a selected loading map for a next cycle of operation. Theselected loading map may be one of a plurality of loading mapsevaluated. The selection may be based on a trial and error process by acore designer and/or by an evaluation result of an objective function.The objective function methodology is disclosed in U.S. application Ser.No. 10/246,716, titled METHOD AND APPARATUS FOR EVALUATING A PROPOSEDSOLUTION TO A CONSTRAINT PROBLEM, by a subset of inventors of thesubject application.

The established bundle groups may serve as a constraint by limiting thenumber of proposed loading maps to be considered (e.g., by either thecore designer and/or the objective function). The constraint is thatfuel bundles may only be exchanged with other fuel bundles of the samebundle group within the same region of symmetry. The region of symmetrymay refer to any of the above-described symmetry regions, including aquadrant (e.g., a quarter of the entire core as implemented in theUnited States), a semi (e.g., half of the entire core as implemented inEurope), an octant, etc. Since fuel bundle exchanges are often the“bottleneck” of the outage (e.g., the duration of the outage may scalewith the number of fuel bundle movements), the duration of the outagemay be reduced by limiting exchanges between fuel bundles (e.g., withinthe region of symmetry) to fuel bundles within the region of symmetrysince these exchanges require less time. Thus, before evaluating aproposed loading map, proposed loading maps including violations of theabove-described bundle group constraints are culled and removed fromconsideration. Then, the reduced set of proposed loading maps may beconfigured for inclusion within an objective function for evaluation bythe core designer.

Therefore, evaluation time (e.g., by the core designer or the objectivefunction) required to select the loading map for the next cycle ofoperation may likewise be reduced since fewer loading maps areconsidered.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the invention.

1. A method of implementing bundle groups as a constraint in anevaluation, comprising: creating a plurality of fuel bundle groups in acurrent loading map; generating a first plurality of proposed loadingmaps to establish potential core loading at a next cycle of operation;filtering the plurality of proposed loading maps to create a secondplurality of proposed loading maps, the second plurality of proposedloading maps satisfying at least one fuel bundle group constraint; andconfiguring an objective function to evaluate the second plurality ofproposed loading maps.
 2. The method of claim 1, wherein the at leastone fuel bundle group constraint includes limiting each fuel bundlemovement between the current loading map and each of the secondplurality of proposed loading maps to exchanges between fuel bundleswithin the same group.
 3. The method of claim 1, wherein the at leastone fuel bundle group constraint includes limiting each fuel bundlemovement between the current loading map and each of the secondplurality of proposed loading maps to exchanges between fuel bundleswithin the same region of symmetry.
 4. The method of claim 3, whereinthe region of symmetry is one of octant, quadrant and semi.